Digital audio files, such as MP3, ATRAC (adaptive transform acoustic coding), WMA (windows media audio), AAC (advanced audio coding), etc. are popular media for listening music or audio dramas, comedies and the like. Digital audio files are generally stored in a storage medium such as a hard disk, CD-ROM, memory card, etc., installed in a small box. Such media have an advantage that, because of the compression technology, the size of each file is smaller than that of a conventional audio format used in a compact disk (CD) ROM. In addition to the audio data, a digital audio file contains tag-data (meta-data) that describe tag information such as, artist names, titles of music, genre of music, etc. Such information is often used by a digital audio player to display music information in a text format to help a user to identify the music.
Portable digital audio players, such as an ipod (Apple, Inc.), are popular due to their capability of storing a large amount of music and their portability. Typically, a user creates a library of favorite music in a portable digital audio player and listens to the music while working, studying, walking, or the like. The user also wants to listen to the music from his collection in the portable digital audio player even when he is driving an automobile or anyway in an automobile without using a headset of the portable digital audio player.
Thus, there is a demand to use such a portable digital audio player in combination with an automobile (vehicle) audio system so that a user can enjoy his preferred music or dramas, etc., stored in the portable digital audio player when the user is driving an automobile. In such an application, because a number of music files in such digital audio players is large, searching a particular audio file poses a significant problem when the user is driving an automobile.
Since the automobile audio system is usually used when the user is driving the vehicle, distraction of user's attention from the driving must be minimized. In particular, for safe driving, visual distraction should be minimized as much as possible when the user searches for next pieces of music stored in the portable digital audio player. Accordingly, there is a need of a new method of searching for desired music files in the portable digital audio player and playing the music files by an automobile audio system with minimum distraction from the driving.